This invention relates, generally, to an improvement in radio system construction and deployment that allows for a higher concentration of radio transceivers to be collocated and more specifically to an Internet access system including a high isolation parabolic horn antenna and other isolation techniques to allow for a high concentration of transceivers at one location thus improving data rates and significantly lowering the cost of deployment of a wireless Internet access system.
As the communications industry continues to evolve, ever-increasing demand for high-speed broadband solutions for communications will result, with the accompanying technologies experiencing a similar demand pattern. While industry analysts predict that 100-megabit speeds will be common by the year 2002, the disclosed system design can assist in delivering these speeds now.
The need for high-speed Internet access within the U.S. is well defined. With respect to Internet applications alone, as of Dec. 1999, there were fewer than 250,000 U.S. customers purchasing DSL services, as compared to more than 30 million Internet customers. The ever increasing need for wireless communication services such as Cellular Mobile Telephone (CMT), Digital Cellular Network (DCN), Personal Communication Services (PCS) and the like, typically requires the operators of such systems to serve an ever increasing number of users in a given service area. As a result, certain types of base station equipment including high capacity Broadband Transceiver Systems (BTS) have been developed which are intended to service a relatively large number of active mobile stations in each cell. Such broadband transceiver system equipment can typically service, for example, ninety-six simultaneously active mobile stations in a single four-foot tall rack of electronic equipment. This base station equipment typically costs less than $2000 to $4000 per channel to deploy, and so the cost per channel serviced is relationally low. But, demand is increasing beyond capacity and downward cost pressures continue to exist.
Numerous patents have attempted to solve these problem such as U.S. Pat. No. 5,970,410 issued to Carney, et al. on Oct. 19, 1999 titled Cellular System Plan Using In Band-Translators To Enable Efficient Deployment Of High Capacity Base Transceiver Systems. This patent describes a wireless system architecture whereby high efficiency broadband transceiver systems can be deployed at an initial build out stage of the system in a cost-efficient manner. A home base station location is identified within each cluster of cells and rather than deploy a complete suite of base station equipment at each of the cells in the cluster, inexpensive translator units are located in the outlying cells serviced by the home base station in which low traffic density is expected. The translators are connected to directional antennas arranged to point back to the home base station site. The translators are deployed in such a way which meshes with the eventually intended frequency reuse for the entire cluster of cells. The translator to base station radio links operate in-band, that is, within the frequencies assigned to the service provider. For example, the available frequency bands are divided into at least two sub-bands, with a first sub-band is assigned for use as a home base station to translator base station communication link and a second sub band is assigned for use by the mobile station to translator communication link. If desired, a third sub-band can then be used for deployment of base transceiver systems in the conventional fashion where the base station equipment located at the center of a cell site communicates only with mobile stations located within that cell. When coupled with efficient frequency reuse schemes maximum efficiency in densely populated urban environments is obtained. According to some arrangements the cells are each split into radial sectors and frequencies are assigned to the sectors in such a manner as to provide the ability to reuse available frequencies. Although frequency reuse schemes can be highly efficient, it requires at least two complete sets of multi-channel transceiver equipment such as in the form of a Broadband Transceiver System (BTS) to be located in each cell.
However, when a wireless system first comes on line, demand for use in most of the cells is relatively low, and it is typically not possible to justify the cost of deploying complex multichannel broadband transceiver system equipment based only upon the initial number of subscribers. Because only a few cells at high expected traffic demand locations (such as at a freeway intersection) will justify the expense to build-out with high capacity Broadband Transceiver System equipment, the service provider is faced with a dilemma. He can buildout the system with less expensive narrowband equipment initially, to provide some level of coverage, and then upgrade to the more efficient equipment as the number of subscribers rapidly increases in the service area. However, the initial investment in narrowband equipment is then lost. Alternatively, a larger up front investment can be made to initially deploy high capacity equipment, so that once demand increases, the users of the system can be accommodated without receiving busy signals and the like. But this has the disadvantage of carrying the money cost of a larger up front investment.
Other various techniques for extending the service area of a given cell have been proposed. For example, U.S. Pat. No. 4,727,490 issued to Kawano et al. and assigned to Mitsubishi Denki Kabushiki Kaisha, discloses a mobile telephone system in which a number of repeater stations are installed at the boundary points of hexagonally shaped cells. The repeaters define a small or minor array that is, in effect, superimposed on a major array of conventional base stations installed at the center of the cells. With this arrangement, any signals received in so-called minor service areas by the repeaters are relayed to the nearest base station.
Another technique was disclosed in U.S. Pat. No. 5,152,002 issued to Leslie et al., wherein the coverage of a cell is extended by including a number of so-called xe2x80x9cboostersxe2x80x9d arranged in a serial chain. As a mobile station moves along an elongated area of coverage, it is automatically picked up by an approaching booster and dropped by a receding booster. These boosters, or translators, use highly directive antennas to communicate with one another and thus ultimately via the serial chain with the controlling central site. The boosters may either be used in the mode where the boosted signal is transmitted at the same frequency as it is received or in a mode where the incoming signal is retransmitted at a different translated frequency.
Additional attempts to improve coverage include spectral efficiency schemes such as disclosed in U.S. Pat. 5,592,490 issued to Barratt, et al., on Jan. 7, 1997 titled Spectrally Efficient High Capacity Wireless Communication Systems which discloses a wireless system comprising a network of base stations for receiving uplink signals transmitted from a plurality of remote terminals and for transmitting downlink signals to the plurality of remote terminals using a plurality of conventional channels including a plurality of antenna elements at each base station for receiving uplink signals, a plurality of antenna elements at each base station for transmitting downlink signals, a signal processor at each base station connected to the receiving antenna elements and to the transmitting antenna elements for determining spatial signatures and multiplexing and demultiplexing functions for each remote terminal antenna for each conventional channel, and a multiple base station network controller for optimizing network performance, whereby communication between the base stations and a plurality of remote terminals in each of the conventional channels can occur simultaneously.
Other methods include specialized propagation techniques such as shown in U.S. Pat. No. 6,058,105 issued to Hochwald, et al. on May 2, 2000 titled Multiple Antenna Communication System And Method Thereof which discloses a communications system that achieves high bit rates over an actual communications channel between M transmitter antennas of a first unit and N receiver antennas of a second unit, where M or N greater than 1, by creating virtual sub-channels from the actual communications channel. The multiple antenna system creates the virtual sub-channels from the actual communications channel by using propagation information characterizing the actual communications channel at the first and second units. For transmissions from the first unit to the second unit, the first unit sends a virtual transmitted signal over at least a subset of the virtual sub-channels using at least a portion of the propagation information. The second unit retrieves a corresponding virtual received signal from the same set of virtual sub-channels using at least another portion of said propagation information.
Unfortunately, each of these techniques has their difficulties and adds additional costs and complexities to the system. With the method, which uses an array of repeaters colocated with the primary cell sites, the implementation of diversity receivers becomes a problem. Specifically, certain types of cellular communication systems, particularly those that use digital forms of modulation, are susceptible to multi-path fading and other distortion. It is imperative in such systems to deploy diversity antennas at each cell site. This repeater array scheme makes implementation of diversity antennas extremely difficult, since each repeater simply forwards its received signal to the base station, and diversity information as represented by the phase of the signal received at the repeater, is thus lost.
The booster scheme works fine in a situation where the boosters are intended to be laid in a straight line along a highway, a tunnel, a narrow depression in the terrain such as a ravine or adjacent a riverbed. However, there is no teaching of how to efficiently deploy the boosters in a two-dimensional grid, or to share the available translated frequencies as must be done if the advantages of cell site extension are to be obtained throughout an entire service region, such as a large city.
Therefore a need exists for a wireless communications system which achieves high bit rates in a cost effective and relatively simple manner.
It is therefore clear that a primary object of this invention is to advance the art of high-speed wireless Internet access system design. A more specific object is to advance said art by providing an improved efficiency antenna and radio deployment system useful for high-speed wireless Internet access.
These and other important objects, features, and advantages of the invention will become apparent as this description proceeds. The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.
What is disclosed is an improvement in the design and deployment of collocated radio transceivers for high-speed wireless Internet access accomplished by increased isolation brought about by wrapping each transceiver in a shield of mild steel, enclosing collocated transceivers and associated equipment in non-reflective enclosures, use of low loss RF coaxial cables, and use of high isolation parabolic horn antennas.